Beaming Light from a Subwavelength Aperture

TLDR

Light usually diffracts in all directions when it emerges from a subwavelength aperture, limiting the size of features usable in photonics. This limitation can be overcome by adding a periodic texture to the exit side of a single aperture in a metal film. The textured aperture emits a narrow, tunable beam with about ±3° divergence, even though the radiating region is only about a wavelength across, and the device occupies ≤1 µm³, indicating broad photonic applications.

Abstract

Light usually diffracts in all directions when it emerges from a subwavelength aperture, which puts a lower limit on the size of features that can be used in photonics. This limitation can be overcome by creating a periodic texture on the exit side of a single aperture in a metal film. The transmitted light emerges from the aperture as a beam with a small angular divergence (approximately +/-3 degrees ) whose directionality can be controlled. This finding is especially surprising, considering that the radiating region is mainly confined to an area with lateral dimensions comparable to the wavelength of the light. The device occupies no more than one cubic micrometer and, when combined with enhanced transmission, suggests that a wide range of photonic applications is possible.